1. Field of the Invention
The present invention relates to polymeric products and to aqueous dispersions of polymeric products. More particularly, this invention relates to polymeric products which contain cationic salt groups and to the preparation of these polymeric products in aqueous medium by addition polymerization techniques.
2. Brief Description of the Prior Art
Aqueous dispersions of acrylic polymers are known in the prior art for use in water-based coating applications. One method of preparing these polymers involves polymerizing acrylic monomers under free radical polymerization techniques in aqueous medium in the presence of surfactant. The surfactants are needed to stabilize the dispersion and are relatively low molecular weight ionic or non-ionic materials which contain both hydrophilic and hydrophobic groups. Surfactants present a problem in subsequent coating applications in that they remain in the film where they can adversely affect the adhesion and the humidity resistance of the film.
Although acrylic polymers can be prepared without surfactant and dispersed in water, for example, by preparing acrylic polymers containing carboxylic acid groups in organic solvent followed by neutralizing the acrylic polymer with base and dispersing the base-neutralized polymer in water, these particular polymers are of low molecular weight and do not have the physical and chemical properties of acrylic polymers prepared directly in aqueous medium in the presence of surfactant.